diff --git a/module/src/main/java/pl/clarin/converter/JSON2XLSX.java b/module/src/main/java/pl/clarin/converter/JSON2XLSX.java
index ca6d6763152b65c17f37809f69686704a467f216..b6e4d087876b1f170edb2c2440a154e2e9bf5e31 100644
--- a/module/src/main/java/pl/clarin/converter/JSON2XLSX.java
+++ b/module/src/main/java/pl/clarin/converter/JSON2XLSX.java
@@ -13,6 +13,7 @@ import java.util.HashMap;
 import org.apache.poi.xssf.usermodel.XSSFRow;
 import org.apache.poi.xssf.usermodel.XSSFSheet;
 import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+import org.json.JSONException;
 
 import org.json.JSONObject;
 
@@ -24,15 +25,25 @@ public class JSON2XLSX {
 
     int key_id = 0;
     HashMap<String,Integer> keys=new HashMap<>();   
+    
+    
     private void process(String fileIn, JSONObject options, XSSFRow row, int column) throws Exception {
         
         String content = new String(Files.readAllBytes(Paths.get(fileIn)));
         JSONObject json = new JSONObject(content);
         for(String key:json.keySet())
-        {  if (!keys.containsKey(key))
-           { keys.put(key, new Integer(key_id++));
+        {  double value = 0;
+           try {
+            value=json.getDouble(key);
            }
-            double value = json.getDouble(key);
+           catch (JSONException e)
+           {
+               continue;
+           }
+           if (!keys.containsKey(key))
+           { keys.put(key, key_id++);
+           }
+            
             row.createCell(column + keys.get(key)).setCellValue(value);
         }